The present invention relates generally to a chain sawing assembly, a saw bar for a chain sawing device and a method of manufacturing such a saw bar, and more particularly to an improved chain saw bar fluid passage system. Such a chain saw bar having an improved fluid passage system may be used to convey lubrication fluid, such as oil, to a chain saw bar sprocket, or used to spray a chemical, such as urea, on a tree being cut by such a chain sawing assembly.
Other chain saw bars having fluid lubrication passages therein have been used to convey lubrication fluid from a reservoir within the chain saw frame housing to remote locations on the chain saw bar. For example, U.S. Pat. Nos. 3,279,508, 3,621,896, 3,044,506, and German Patent No. 2,321,316 each disclose a laminated bar design constructed with two outer side plates surrounding an inner core plate. The inner core plate typically has at least one void therein which receives oil from holes extending through one or both of the outer side plates. The oil is delivered through the center core plate void to various outlet points, such as a saw bar guide groove which receives the guide links of an endless cutting chain, or a sprocket rotatably mounted at a nose end of the bar.
U.S. Pat. No. 4,819,332 to Sugihara et al. discloses a laminated bar system providing lubrication to a nose sprocket bearing assembly. The lubrication fluid is delivered through a void within the core plate from the frame housing reservoir to an auxiliary reservoir formed by an enlarged void within the core plate. This design requires external tubing to bridge the gap between the main portion of the saw bar and the sprocket to deliver the oil from the auxiliary reservoir to the sprocket bearing assembly. This external tubing enters the auxiliary reservoir through a hole within one of the outer side plates and delivers the oil to the sprocket bearing surface through a second hole in the side plate. A recess is formed in the exterior surface of the side plate to receive this external tubing.
U.S. Pat. Nos. 3,578,779 to Ishizaki, 2,913,002 to Nielsen, and 3,185,191 to Olsen, each disclose a saw bar lubrication system having a solid bar with an oil passageway formed in the bottom of the chain guide groove. This oil passageway typically has outlet openings near the nose end of the bar.
German Patent No. 908,296 discloses a solid saw bar lubrication system delivering oil to the cutting chain guide groove using a saw bar having a passage-forming insert fitted therein. A channel is milled into one side of the guide bar along a longitudinal axis. The channel extends from a proximate end inlet at the chain saw housing end of the bar to a distal end at a point spaced apart from the nose end of the bar. A solid elongated insert piece is then fitted into this channel extending between the proximate and distal ends. The insert piece and channel are each constructed to form an oil passageway therebetween, with the passageway stopping short of the distal end of the channel and insert piece. Transverse holes are drilled from the guide groove through the solid saw bar and a portion of the insert piece to interconnect the central oil passageway with the bottom of the chain guide groove.
These known saw bars suffer a variety of disadvantages. Generally, laminated bars are expensive and difficult to manufacture, requiring precise fits, close tolerances and a multiplicity of parts. Also, the known saw bars do not include means for applying a fluid to the surface of an item, such as a tree, being cut by the saw assembly.
Furthermore, saw bars are typically used at remote locations, and reliability of the saw bar, as well as the overall chain sawing assembly, is of the utmost importance to the operator. For example, if the saw bar becomes bent during transportation or use, the known saw bars cannot be satisfactorily bent back into a usable flat shape by an operator having few repair tools in the field or forest.
Saw bars are particularly vulnerable to damage when used with a tree harvester, but may produce superior results compared to other tree harvester cutting systems. For example, some known tree harvesters have arms that grip and support the upper portion of the tree while shears on the harvester sever the tree near the base. The pinching motion of the shears during cutting often splinters the tree causing butt damage to the wood. Alternatively, disk saws are be used to cut the tree base. However, the disk saws are easily damaged and costly to replace when dulled. When a cutting chain becomes dull, only the relatively inexpensive chain need be replaced, which makes chain sawing systems preferable to disk saws. To enhance the reliability of a chain saw bar and increase the desirability of using a chain cutting system in tree harvesters, the saw bar field repair problem must be overcome.
Thus, a need exists for an improved cutting assembly system and for an improved saw bar for use therewith, as well as for an improved method of manufacturing such a saw bar, which are not susceptible to the above limitations and disadvantages.